1. Field of the Invention
The present invention relates to a fixture for holding components during electro-chemical processing and, more particularly, is directed to a racking fixture designed to ensure uniform electrochemical processing over all surfaces of a component.
2. Background Information
Metallic components critical to a mechanical operation are often electro-chemically treated to ensure their reliability. For example, components critical to the performance of an aircraft are coated with cadmium to protect the components from corrosion or other related damage caused by exposure to an extreme environment. Another example of electrochemical processing would be copper plating a component to prevent a build-up of carbon which would otherwise occur in a high temperature environment.
The electrochemical processing of a component to enhance its reliability is often a complex process. For example, to electroplate components with cadmium, they are first cleaned in an emulsion cleaner, such as Brulan 815 GD, and soap to remove all oil deposits. Then the components are double rinsed and cleaned in an alkaline cleaning solution, such as IsoPrep 44L-ND. The components are then double rinsed and treated with IsoPrep 172, where they undergo a "forward/reverse" treatment in which they are polarized first at one polarity and then in the opposite polarity. The forward/reverse treatment assists in removing any remaining unwanted deposits. The components are then rinsed again and immersed in a solution of hydrochloric acid to activate the metallic portions of the components. The activated metal of the components is then double rinsed again and finally dipped into a tank 200 containing cyanide, as shown in FIG. 1.
The tank 200 is typically electrically connected to a main rectifier 202, which produces approximately 1000 amps of current and 3 volts potential within the cyanide solution. The negative terminal of the rectifier 202 is coupled to negative terminal contacts 204a and 204b, while the positive terminal of the rectifier 202 is coupled to positive terminal contacts 206a and 206b. Extension positive buses 208a and 208b are placed lengthwise across the tank 200 to make contact with the respective positive terminal contacts 206a and 206b. Anode baskets 210a-210f are suspended from the positive buses 208a and 208b by conductive metal cables 211a-211f The anode baskets 210a-210f typically contain three or four cadmium balls.
A rack 212, including current transmitting support members (i.e. negative buses) 214a-214e, is seated upon the tank 200. The support members 214a-214e are physically, as well as electrically, connected to negative terminal contacts 204a and 204b. Two parallel projections 216a and 216b extend downward into the tank 200 from the support members 214a-214e. Two or more component-holding shelves 218a and 218b are positioned between the parallel projections 216a and 216b and supply a negative electric charge from the main rectifier 202 to each of the components supported within the rack 212.
Many of the components processed in this manner, such as component 220 in FIG. 2, have blind holes, i.e., holes which dead-end within the component 220. For example, in the component 220, holes 222a and 222b are both blind holes. Unfortunately, with the above-described process, hydrogen and oxygen gas generated during the electro-chemical treatment form bubbles within the blind holes 222a preventing proper cleaning and deposition of electroplate or anodonic coatings. Further, because of the structure of the blind holes 222a and 222b, they also usually receive insufficient potential for proper electroplating. Consequently, the components 220 need to be further processed within a secondary electroplating device 223, shown in FIG. 3.
The secondary electroplating device 223 includes cathode holders 224a-224f, each having holes filled with cyanide solution and coupled to a negative terminal of a rectifier (not shown). Each of the blind major holes 222a of the components 220 are filled by hand with cyanide solution and the components 220 are positioned into a respective one of these cathode holders 224a-224f Then, a series of cadmium anodes 226a-226f, which are held in position by plate 227, are stuck into the holes 222a of the respective components 220. Current is then applied to each of the anodes 226a-226f to deposit the appropriate amount of cadmium into the holes 222a.
Unfortunately, the secondary electroplating process performed by the device 223 can only handle a small number of the components 220 at a time. Also, the process potentially exposes a worker to direct contact with a toxic cyanide solution. Thus, the present process requires an extensive number of man hours to perform and may be hazardous as well.
Consequently, in the art of electroplating and electrochemical processing, there is a need for a device or racking fixture which can uniformly electroplate a component having blind holes without the use of a secondary process.